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  <div class="section" id="creating-rectilinear-meshes-for-ls-dyna">
<h1>Creating Rectilinear Meshes for LS-DYNA<a class="headerlink" href="#creating-rectilinear-meshes-for-ls-dyna" title="Permalink to this headline">¶</a></h1>
<p>Most of the meshes used in first-pass FEM simulations of acoustic
radiation force excitations are large rectangular solids with either
uniform cubic 3D elements, or elements with a slight aspect ratio. This
document provides an overview of the process of generating a 3D mesh
using tools in this repository (<code class="docutils literal notranslate"><span class="pre">fem/mesh</span></code>).</p>
<div class="section" id="syntax">
<h2>Syntax<a class="headerlink" href="#syntax" title="Permalink to this headline">¶</a></h2>
<p><code class="docutils literal notranslate"><span class="pre">mesh/GenMesh.py</span></code> will generate a the rectilinear mesh with
user-specified properties. You can specify two opposing corner vertices
of the mesh (<code class="docutils literal notranslate"><span class="pre">--n1</span></code> and <code class="docutils literal notranslate"><span class="pre">--n2</span></code>), the element density on each edge
(x, y, z), and the names of the output files for node and element
definitions.</p>
<p>Run: <code class="docutils literal notranslate"><span class="pre">python</span> <span class="pre">GenMesh.py</span> <span class="pre">--help</span></code> for detailed input syntax.</p>
</div>
<div class="section" id="coordinate-system">
<h2>Coordinate System<a class="headerlink" href="#coordinate-system" title="Permalink to this headline">¶</a></h2>
<p>Meshes in this code base utilize different conventions for the FEM
portion of the code compared to the Field II simulation component.
LS-DYNA mesh conventions are:</p>
<ul class="simple">
<li>x - elevation</li>
<li>y - lateral</li>
<li>z - axial (negative, with transducer face &#64; z = 0)</li>
</ul>
<p>Maintaining a right-hand rule convention, for a quarter-symmetry model,
x would span a negative range of values for positive 7 values.</p>
</div>
<div class="section" id="units">
<h2>Units<a class="headerlink" href="#units" title="Permalink to this headline">¶</a></h2>
<p>The typical unit system for the mesh is CGS, and this will be assumed in
the code that passes data to/from Field II.</p>
</div>
<div class="section" id="next-steps">
<h2>Next Steps<a class="headerlink" href="#next-steps" title="Permalink to this headline">¶</a></h2>
<ol class="arabic simple">
<li>Your mesh will be used as an input to Field II to simulate the
acoustic radiation force at nodes. This is done using
<code class="docutils literal notranslate"><span class="pre">field/field2dyna</span></code>.</li>
<li>You will need to generate boundary conditions for your mesh
(<code class="docutils literal notranslate"><span class="pre">mesh/bc.py</span></code>)</li>
<li>You may want to create structures in your mesh with different
material properties (<code class="docutils literal notranslate"><span class="pre">mesh/CreateStructure.py</span></code>)</li>
</ol>
</div>
</div>


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  <h3><a href="index.html">Table Of Contents</a></h3>
  <ul>
<li><a class="reference internal" href="#">Creating Rectilinear Meshes for LS-DYNA</a><ul>
<li><a class="reference internal" href="#syntax">Syntax</a></li>
<li><a class="reference internal" href="#coordinate-system">Coordinate System</a></li>
<li><a class="reference internal" href="#units">Units</a></li>
<li><a class="reference internal" href="#next-steps">Next Steps</a></li>
</ul>
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